"Intermediate notions between [[normal subgroup]] and [[perfect normal subgroup]]","Intermediate notions between [[normal subgroup]] and [[perfect normal subgroup]]#"
"Normal subgroup whose focal subgroup equals its derived subgroup","Normal subgroup whose focal subgroup equals its derived subgroup"
"Subgroup realizable as the commutator of the whole group and a subgroup","Subgroup realizable as the commutator of the whole group and a subgroup"
"Upper join of characteristic subgroups","Upper join of characteristic subgroups"